WASHINGTON, Sept 2 (Reuters) - Democrats on Sunday criticized the Trump administration for refusing to release thousands of documents on Brett Kavanaugh ahead of this week's upcoming Senate hearings on his nomination to the U.S. Supreme Court.

Kavanaugh, nominated by President Donald Trump, worked in the White House under former President George W. Bush, whose lawyers combed through documents from that time and decided that 27,000 of them were protected under "constitutional privilege."

The White House directed them not to hand them over to the Senate Judiciary Committee, one of Bush's lawyers said in a letter to the chairman of the Senate Judiciary Committee, which will host the hearings scheduled to start on Tuesday.

Another 102,000 pages of documents related to Kavanaugh's record were not turned over for other reasons. The committee has had access to more than 415,000 pages on Kavanaugh's background, the lawyer said in the letter.

Dick Durbin, the No. 2 Senate Democrat, said in an interview aired on "Fox News Sunday" that the White House's citation of privilege on the documents was the first time that had occurred.

"There has been more concealment of documents that are concerning his public service and his position on issues than ever in the history of the United States ... If he's so proud of his conservative credentials, show us the record," Durbin said.

Democratic Senator Amy Klobuchar, a Judiciary Committee member, echoed Durbin's concerns in an interview with NBC's "Meet the Press" on Sunday, saying, "This is not normal."

Republicans have dismissed Democrats' concerns over lack of access to portions of the record on Kavanaugh's background, arguing their criticism is politically motivated.

"Democrats have more than enough information to understand that this is a highly qualified jurist that should be the next Supreme Court justice," Wisconsin U.S. Senator Ron Johnson, a Republican, said in an interview on ABC's "This Week."

Trump nominated Kavanaugh to be a justice on the U.S. Supreme Court to replace the retiring Justice Anthony Kennedy on July 9.

Kavanaugh must win a majority of the 100-seat Senate to approve his nomination. Most Republicans, who hold a slim majority in the chamber, are expected to back him.